Styrene-butadiene rubber (SBR) has four different repeat units of styrene, cis-1,4-, trans-1,4-, and 1,2-uints. Influence of the 1,2-unit content on the retraction behaviors of SBR vulcanizates reinforced with silica or carbon black was studied. The retraction behaviors were compared in terms of the filler systems and the microstructures of SBR. The silica-filled vulcanizates containing a coupling agent showed nearly the same retraction behaviors as the carbon black-filled ones, but the silica-filled vulcanizates without a coupling agent were recovered slower than the carbon black-filled ones. The vulcanizates with lower 1,2-unit content started to recover at lower temperature than that with higher 1,2-unit content. The recovery rate increased with increase of the 1,2-unit content of SBR. The experimental results were explained with the polymer-filler interactions, filler dispersion, glass transition temperature, and modulus. (c) 2006 Wiley Periodicals, Inc.